The U.S. envoy to Libya, Christopher Stevens, and three other diplomats were killed when suspected Libyan religious extremists stormed the U.S. consulate in Benghazi. Read the latest news here.

Demonstrators attacked a U.S. consulate in Libya, killing one American, and breached the walls of the U.S. Embassy in Cairo, amid angry protests over a film by a U.S. producer that mocks and insults the Prophet Muhammad.

The footage, which depicts the Islamic Prophet Muhammad as a womanizing fraud, was posted on YouTube in early July under the user name Sam Bacile.

He characterized the film as a political effort to call attention to the hypocrisies of Islam. It has been promoted by Terry Jones, the Florida pastor whose burning of Qurans previously sparked deadly riots around the world.

Egyptian protesters climbed the walls of the U.S. Embassy in Cairo and replaced the flag with a black standard bearing an Islamic inscription, in protest of a film deemed offensive to the Prophet Muhammad. Matt Bradley has details on The News Hub.

Obama Comments on Attack on U.S. Embassy in Libya

President Barack Obama speaks in the White House Rose Garden on the death of the U.S. Ambassador to Libya, Christopher Stevens.

In Benghazi, Libya, several dozen gunmen from an Islamist group, Ansar al Sharia, attacked the consulate with rocket-propelled grenades to protest the film, a deputy interior minister for the Benghazi region told the Al-Jazeera network. A government brigade evacuated the consulate, after which militants set it on fire, said the minister, Wanees Sharef.

One State Department officer was killed in the attack in Benghazi, Secretary of State Hillary Clinton said Tuesday night.

Mrs. Clinton said the State Department was working with Libyans to secure the compound and protect Americans in Libya.

To the east, in Cairo, a crowd of some 2,000 people gathered at the Embassy to protest the video. Some of them climbed the embassy walls late Tuesday, pulling down and burning an American flag.

Hours after nightfall, dozens of young men remained standing on top of the embassy walls, shouting into megaphones. One of the youths climbed up the flagpole to hoist a black banner emblazoned with the Muslim profession of faith in white letters—"There is no God but God and Muhammad is His Messenger"—a standard used by hardline Islamist groups throughout the world.

At the Cairo Embassy, Egyptian police had removed demonstrators from the grounds, the State Department said. The Egyptian foreign ministry said that the government bears full responsibility for the protection of foreign embassies on Egyptian soil.

The flashpoint appeared to be the film about the Prophet Muhammad, portions of which in recent days have been circulating on the Internet. Contravening the Islamic prohibition of portraying the prophet, clips from the film show him not only as flesh and blood—but as a homosexual son of undetermined patrimony, who rises to advocate child slavery and extramarital sex, for himself, in the name of religion.

"The United States deplores any intentional effort to denigrate the religious beliefs of others," Mrs. Clinton said Tuesday night.

"But let me be clear: There is never any justification for violent acts of this kind," she said in reference to the attacks.

The man who claimed to be the film's writer, director and producer, identified himself as Sam Bacile, a name that was subsequently believed to be a pseudonym. He said that he wanted to showcase his view of Islam as a hateful religion. "Islam is a cancer," he said in a telephone interview from his home. "The movie is a political movie. It's not a religious movie."

He said he worked with about 60 actors and 45 crew members and made the two-hour movie in three months last year in California.

The film has been promoted by Dr. Jones, who said Tuesday that he planned to show a 13-minute trailer that night at his church in Gainesville, Fla.

"It is an American production, not designed to attack Muslims but to show the destructive ideology of Islam," he said in a statement. "The movie further reveals in a satirical fashion the life of Muhammad."

In the hours leading up to the rally in Cairo, the U.S. Embassy there invoked the First Amendment rights to free speech, but said the film constituted an abuse of those rights.

"The Embassy of the United States in Cairo condemns the continuing efforts by misguided individuals to hurt the religious feelings of Muslims—as we condemn efforts to offend believers of all religions," it said in a statement. "Respect for religious beliefs is a cornerstone of American democracy. We firmly reject the actions by those who abuse the universal right of free speech to hurt the religious beliefs of others."

It wasn't clear whether the brief invasion of U.S. Embassy grounds in Cairo—one of the largest diplomatic facilities in the world—would damage America's relationship with the new Islamist-backed Egyptian administration.

With Egypt's economy in a tailspin, its new Islamist president, Mohammed Morsi, has taken pains to prove that he and his powerful Muslim Brotherhood backers can remain a reliable partner to the West. Two weeks ago, a team of U.S. diplomats were negotiating terms under which the U.S. could forgive the first tranche of $1 billion in debt.

On Tuesday, as protesters attacked, a trade delegation of more than 100 American businessmen were wrapping up a four-day visit meant to stoke investor interest in postrevolutionary Egypt.

"This isn't the optic that [the Brotherhood] are going to be particularly pleased with," said Michael Hanna, an Egypt expert at the New York-based Century Foundation. "The timing is unfortunate for everybody involved."

The man who claimed to be the filmmaker, said he posted the trailer for his film on YouTube in early July. But it had largely escaped attention until recent days, when activists on Twitter pointed to clips that included actors in anachronistic costumes, near flimsy sets and often stumbling through lines. Egyptian clerics began widely condemning the footage.

In Cairo, protesters said they rallied to the embassy at the prompting of Islamist Facebook groups and hard-line Salafi preachers who frequently preach on Islamist satellite channels.

Early Tuesday evening in Cairo, the crowd of mostly male Islamists converged outside the heavily guarded U.S. mission. Some scaled the embassy's concrete walls but were met by rubber bullets fired by embassy guards, some witnesses reported.

A U.S. Embassy official denied that embassy guards had fired on the protesters.

Protesters destroy an American flag ripped down from the U.S. Embassy in Cairo on Tuesday, as they put a black flag in its place. Mohammed Abu Zaid/Associated Press

Protest leaders said they convinced the young men to leave the embassy grounds without further violence. But after darkness fell, dozens of young men remained. Some of the demonstrators spray painted the slogan on the embassy's walls as hundreds of police, clad in riot gear, sat by.

The movie has been promoted in the U.S. by conservative Coptic Christians, including Morris Sadek, who runs a small group called the National American Coptic Assembly. "The violence that it caused in Egypt is further evidence of how violent the religion and people are and it is evidence that everything in the film is factual," Mr. Sadek said in a telephone interview from his Washington home.

Coptic leaders from around the world denounced the film and its portrayal of Islam.

While protesters in Cairo said they understood American laws on free expression, they saw them as secondary to their religious practice. "Freedom of belief is more important than freedom of expression," said Ashraf Ibrahim, 34, who was at Tuesday's protest.

Egyptian society would never fully adopt the Western notion of "liberalism" despite American-led efforts to impose such ideals on Arab nations, said Mr. Ibrahim's friend, Ahmed Hamza. "The American system will fall," he said.

Like many of the demonstrators, Mr. Hamza and Mr. Ibrahim wore short beards that characterize conservative Muslims.

Though the film was the focus of demonstrators' outrage, the spirited protest amounted to more of a general outpouring of grievances against U.S. policy in the Islamic world. Several signs and chants decried the U.S.-led invasions of Iraq and Afghanistan, as well as American support for Israel.

Many recalled the attacks of Sept. 11, 2001, that killed thousands of U.S. citizens 11 years earlier.

"Obama! Obama! We are all Osama!" went one chant, referring to Osama bin Laden, the late head of Al Qaeda, the militant Islamist organization widely believed to be responsible for the 9/11 attacks.

Mohammed Al Zawahiri, the brother of Al Qaeda leader Ayman Al Zawahiri, was among those who attended the rally early in the evening. The younger Mr. Zawahiri, who has renounced violence and has stylized himself as an intermediary between Islamists and the West, was released from an Egyptian jail in March after serving 10 years on charges of militancy.

Corrections & Amplifications An earlier version of this article included claims by the person who identified himself as Sam Bacile that he is an Israeli-American and that he raised $5 million from about 100 Jewish donors to fund the film. Those claims weren't confirmed and should not have been included in the article. In addition, the article has been updated to note that the name used by the person appears to be a pseudonym, based on subsequent reporting.

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